Modern wind turbines are designed for series production. Modularization is used as a means to establish a lean production of sub-assemblies. It is therefore desirable to modularize the control system in accordance with the wind turbine modularization to enable sub-assembly manufacturing and testing in a lean production set-up.
Modern power plants comprise not only wind turbines but also other facilities as e.g. power measurement systems, phase compensation systems, metrology systems, switch gear systems and energy storage systems. Such systems can also be modularized to enable sub-assembly manufacturing and testing in a lean production set-up. The systems themselves can be considered modules in a wind power plant and thus hold distributed control nodes. It is considered beneficial to modularize the control system in accordance with the system modularization.
Modern wind turbines and other power plant systems are subject to high requirements to availability and power production and consequently production stops caused by the control system are considered unacceptable. The reliability requirements to wind turbine control systems are therefore very high. Fault-tolerant based control systems are means to obtain desired reliability and safety requirements.
Modern wind turbines are subject to high safety requirements. Large modern wind turbines have high demands on functional safety. The control system must have functional safety properties to support the demands. Energy storage facilities, power converter systems, power switch gears systems and other power plant systems may also have high demands on functional safety as the impact of failures can be severe both in relation to human health and damage to assets.
Fault-tolerant control systems for wind power plants are typically implemented as redundant systems comprising duplicates of various critical plant modules/devices. In case a critical plant module/device fails its functionality is taken over by a similar plant module/device.
U.S. 2009/0309360 and U.S. 2009/0309361 both discuss a method and a system for controlling a wind energy park. In U.S. 2009/0309360 and U.S. 2009/0309361 a main communication unit controls a number of prioritised control units. In case a given control unit with a given priority fails, the main communication unit selects a lower prioritised control unit to take over the functionality of the defective control unit.
It is a disadvantage of the method and system suggested in U.S. 2009/0309360 and U.S. 2009/0309361 that the main communication unit selects which control unit to take over in case another control unit breaks down or in any other way malfunctions. However, in case the main communication unit itself breaks down, no replacement unit is available.
Thus, the control method and the control system suggested in U.S. 2009/0309360 and U.S. 2009/0309361 can not be considered a fault-tolerant control method/system—at least not on the main controller level. Moreover, the control method and the control system suggested in U.S. 2009/0309360 and U.S. 2009/0309361 can not be considered safe as no safety features are implemented.
It may be seen as an object of embodiments of the present invention to provide a distributed control system with inherent fault-tolerant and safety-related properties for wind power plant applications.